The present invention pertains to an injection unit, particularly to an injection unit with a dosing device, by means of which a dose or quantity of a substance to be discharged from or with the aid of the injection unit can be adjusted.
Various injection units, particularly also pin-shaped or pen-shaped injection units, are known from the prior art. For example, WO 93/07922 A1 discloses such a pin-shaped or pen-shaped injection unit. The pen comprises a dosing device and a delivery apparatus that are coupled to one another by means of a two-part unidirectional coupling 20/21, wherein the coupling is realized by means of asymmetric toothings that engage into one another and the engagement is promoted by means of a spring. In this case, a coupling input element 20 features a toothing that is axially directed in the distal direction. A coupling output element 21 features a complementary toothing. The two coupling elements are arranged coaxial to the longitudinal axis of the pen and realized such that they are rotatable relative to the housing of the pen. The individual teeth of the toothings have two flanks, wherein the two flanks have different inclines. One flank points in the axial direction and the second flank has an incline relative to the longitudinal axis. When the coupling is engaged, the axially aligned flanks prevent a relative rotation between the coupling input element 20 and the coupling output element 21 in one direction, whereas the second, inclined flanks allow a relative rotation in the opposite direction.
In order to adjust a dose to be administered, the dosing knob 14 of the dosing device is screwed out of the housing of the unit together with the dosing sleeve 15. In this case, the coupling input element 20 is arranged non-rotatably relative to the dosing knob 14, and the coupling output element 21 is arranged non-rotatably relative to the delivery apparatus. When the dose is increased, the pen is designed in such a way that a relative rotation can take place between the coupling input element 20 and the coupling output element 21. The inclined flanks of the coupling toothings slide over one another in this case, wherein the coupling input element 20 is axially moved against the spring force. When the tips of the teeth slide over one another, the coupling input element 20 springs back into its axial starting position along the axially aligned flanks and generates an audible click. When the dosing knob 14 is screwed back into the housing, the unidirectional coupling prevents a relative rotation between the dosing device and the delivery apparatus due to the axially aligned tooth flanks on the coupling elements 20, 21, wherein the rotation of the dosing knob is therefore transmitted to the delivery apparatus and the discharge of product from the pen can take place. In order to correct the dose, the engagement between the coupling elements 20, 21 has to be manually separated against the spring force. Once the engagement is separated, the dosing device can be moved back into its starting position independently of the delivery apparatus. In order to carry out this type of dose correction, the person using the injection unit must be skilled and powerful because both hands are required for separating and maintaining the engagement in the separated position, i.e. against the spring force. In the released state, the dosing sleeve also has to be screwed back. When the dosing sleeve is screwed back and the engagement is separated, no feedback for the user in the form of a clicking sound is therefore generated.
FIGS. 15-17 of EP 1003581 B1 also show a pen-shaped injection unit. This injection unit features a bidirectional coupling between the dosing device and the delivery apparatus. The dosing device comprises a dosing sleeve 80 with a dosing knob 81 arranged on the sleeve. The dosing sleeve 80 can be coupled to the driver tube 85 of the delivery apparatus by means of a bushing 82. The coupling consists of a coupling input element (not shown) that is rigidly arranged on the dosing sleeve 80 and a coupling output element 93 that is also referred to as rosette and is rigidly arranged on the bushing 82. The coupling is engaged by pushing the discharge button 88 in the distal direction, and it remains non-positively engaged as long as the discharge button is not actuated. The coupling input element and the coupling output element feature a toothing that, in principle, allows a relative rotation, namely even if the coupling elements contact one another due to the weights. As long as the coupling is not engaged due to an actuation of the discharge button, this allows a dosing motion in order to increase the dose, as well as to correct the dose. In the embodiment known from the prior art, no clicking sound is generated in the bidirectional coupling, so that a clicking function has to be realized separately at a different location in the unit.
It is the objective of the present invention to make available an injection unit of the above-described type, i.e. an administration unit with a dosing device and a delivery apparatus that can be separably coupled to one another by means of a coupling mechanism, which has a simple design and provides the user with feedback that can be perceived in an improved fashion during the dose adjustment and/or the correction of excessively adjusted doses.
This objective is attained by means of the object with the characteristics as claimed at least by the independent claims. Other advantageous embodiments are disclosed in the dependent claims.